1. The Field of the Invention
The present invention generally relates to tools, such as drilling, mining, and industrial tools. More particularly, the present invention relates to wear resistant tools and to methods of making and using such tools.
2. Discussion of the Relevant Art
Many drilling, mining, and industrial tools include bodies or pads formed from tungsten carbide (WC) or other wear resistant materials to provide wear resistance and increased tool life. For example, many types of earth-boring tools (such as drill bits and reamers) include a bit body which may be made of steel or fabricated from a hard matrix material such as tungsten carbide (WC). In some cases, a plurality of cutters (e.g., PCD, TSD, surface sets) is mounted along the exterior face of the bit body. The cutters are positioned so that, as the bit body rotates, the cutters engage and drill the formation. Alternatively, the body can comprise the cutter such as with impregnated drill bits.
During drilling the bit bodies of such earth-boring tools can be exposed to high-velocity drilling fluids and formation fluids which carry abrasive particles, such as sand, rock cuttings, and the like. Such abrasive particles can wear down the bit bodies of the earth boring tools, resulting in lost cutters or even failure of the body.
While steel body bits may have toughness and ductility properties which make them resistant to cracking and failure due to impact forces generated during drilling, steel is more susceptible to erosive wear. Tungsten carbide or other hard metal matrix body bits have the advantage of higher wear and erosion resistance as compared to steel bodies. Bodies formed from tungsten carbide or other hard metal matrix materials; however, can lack toughness and strength. Thus, bodies formed from tungsten carbide or other hard metal matrix materials can be relatively brittle and prone to cracking when subjected to impact and fatigue forces that may be encountered during drilling. This can result premature failure of the body. The formation and propagation of cracks in the matrix body may result in the loss of one or more cutters. A lost cutter may abrade against the body, causing further accelerated damage. Furthermore, even tungsten carbide bodies are subject to wear and eventually need to be replaced.
Bodies formed with sintered tungsten carbide may have sufficient toughness and strength for a particular application, but may lack other mechanical properties, such as erosion resistance. Thus, previous efforts have relied on combinations of materials to achieve a balance of properties. Additionally, use of materials having wide particle size distributions have been relied upon so as to achieve a close packing of the carbide wear particles to increase wear resistance.
Other types of drilling tools, such as reamers, drill string stabilizers, wear pads, etc. are susceptible to wear during use. It is common to set carbide or diamond elements in such tools to increase wear resistance and maintain the gauge of the tool. The setting of carbide or diamond elements in such tools can be difficult and can otherwise increase manufacturing time and costs. Furthermore, locations not covered by these elements are still subject to relatively rapid wear.
Percussive drilling tools are often formed from high strength steel bodies. The high strength steel bodies provide the percussive drilling tools with the ductility to be subject to high shock and percussive forces during drilling. Such high strength steel bodies; however, do not have particularly high wear resistance.
In addition to the foregoing, wear resistant pads or other components are frequently added to high wear areas of earthmoving tools and machines, mining tools, and industrial tools that contact abrasive materials, such as rock. For instance, hard facing WC is often added to teeth on front-loader buckets and other tools. Commonly, such wear pads are formed from tungsten carbide to provide superior wear resistance compared to steel. Unfortunately, wear pads can also experience some of the problems discussed above. For example, conventional wear pads can be relatively brittle and prone to cracking when subjected to impact and fatigue forces.
Accordingly, there exists a need for a new composition for tools to increase resistance to wear, while also maintaining other properties such as high strength and toughness.